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Tropical cyclonic systems are generally referred to as tropical storms. They are better known by their regional names, such as hurricanes in the Caribbean and North America, or typhoons in parts of Asia. They form near the equator over larger bodies of warm waters that evaporate from the ocean surface and fuel these emerging storm systems. Their strong winds and heavy rainfalls frequently become part of our news as they often put large numbers of human livelihoods at risk.
Recent studies show that the number of tropical cyclones (as well as tropical cyclone intensity) over the past decades has increased. Tracks of tropical storms collected over a longer period can indicate where such storms occur most frequently. The records used in this issue’s visualisation covers data from 1945 to 2008.

The 20th session of the Conference of the Parties and the 10th session of the Conference of the Parties serving as the Meeting of the Parties to the Kyoto Protocol is held from 1 to 12 December. For COP 20 / CPM 10 delegates from around the world increased their carbon footprint by heading to Lima, Peru, to hopefully produce more than just hot air. So again it is time to speak about the weather…or climate.

Time again to talk about the weather: Britain is suffering under heatwave conditions (also known as summer in other parts of the world), with the ongoing high temperatures and developing clouds going along with an increased humidity slowly increasing the risk for thunderstorms. Thunderstorms are not an uncommon phenomenon on the British Isles, but they are much less common and much less severe compared to other regions experiencing similar conditions much more frequently and more intensively. The Met Office explains that “Owing to the fact thunderstorms are created by intense heating of the earth’s surface, they are most common in areas of the globe where the weather is hot and humid. Land masses therefore experience more storms than the oceans and they are also more frequent in tropical areas than the higher latitudes. In the UK thunderstorms are most common over the East Midlands and the south-east.”
As it happens to be, the part most prone to thunderstorms in Britain is also the most densely populated region. Comparing this to other parts of the world, it can be seen that some of the most risky regions are also some of the very densely populated places. In Europe, which is overall densely populated in many parts, the most affected areas are the people living in the Mediterranean countries, although the European population in general is amongst the least affected by thunderstorms when comparing this to areas such as the southern edge of the Himalayas in India – densely populated and experiencing very intensive thunderstorms. These details only emerge when changing the projection of data collected on lightning flashes from a conventional land area map (where this part of India for instance remains comparably small) to a gridded population cartogram. The following map shows the intensity of lightning flashes displayed as the number of flashes per square kilometre per year in each of the grid cells, while the distortion of the grid cells reflects the global population distribution, so that the most and least exposed populations are highlighted in this visualisation:

In the face of unprecendented occurences of extreme weather, loss of species, and pollution, it is clear that climate change is affecting our planet. We cannot afford to wait any longer to act. This quote from the Earth Day 2013 website outlines the theme for this year’s Earth Day campaign which runs under the motto Climate change has many faces.
As the Earth Day campaign points out, the stories of the impact of climate change are extremely diverse: “A man in the Maldives worried about relocating his family as sea levels rise, a farmer in Kansas struggling to make ends meet as prolonged drought ravages the crops, a fisherman on the Niger River whose nets often come up empty, a child in New Jersey who lost her home to a super-storm, a woman in Bangladesh who can’t get fresh water due to more frequent flooding and cyclones.”
All these tales have one thing in common: They are a story of our impact on planet Earth, but equally of the impact of a changing planet on human’s lives. Our species has become one that is not just living in the natural environment, but is one factor that changes the environment to a level that no other species did before. This is happening to an extent that geologists discuss whether this can be seen as a new geologic era. Nobel Prize laureatePaul Crutzen started promoting the idea of the so-called Anthropocene, a concept that has now left the scientific world and is increasingly entering the public debate regarding issues of global sustainability and humanity’s impact. Anthropocene.info is a project initiated by the International Geosphere-Biosphere Programme (IGBP) that aims to “to help visualize and better understand humanity’s geographic imprint in recent time.” Not only is it important to find better ways of understanding the complex interrelations of humans and their natural environment, to which visualisation can contribute, but also is it important to create a public understanding of issues relating to the challenges connected to global change.
Here is one example of a more challenging view existing knowledge that demonstrates how changing the view can make us rethink the way our natural environment is shaped. According to research by the US National Office of Oceanic and Atmospheric Research, “[t]he strongest hurricanes in the present climate may be upstaged by even more intense hurricanes over the next century as the earth’s climate is warmed by increasing levels of greenhouse gases in the atmosphere. Most hurricanes do not reach their maximum potential intensity before weakening over land or cooler ocean regions. However, those storms that do approach their upper-limit intensity are expected to be slightly stronger in the warmer climate due to the higher sea surface temperatures.”
This is relevant due to the impact of more frequent flooding and cyclones on humans mentioned earlier. So where are these spaces where this is relevant. We know from historic records where there are tropical storm tracks, and the emerging pattern on a normal world map may be familiar to some of us (see here). But what if we change the perspective and focus on the actual areas that have the highest density of tropical storm occurrences. Using the records from 1945 to 2008, this intensity can be turned into quantities which are suitable for visualisation using the gridded cartogram technique. The following map shows a gridded cartogram of tropical storm intensity visualised over land based on a 0.25 degree grid. The larger a grid cell, the more tropical storm activity has there been over the past >60 years, indicating where the most affected areas of tropical cyclones (with a sustained wind speed of ver 40 mp/h) has been and how the climate patterns shape the world in a highly relevant issue of the Anthropocene:

Where rain (or more precisely: precipitation) is affecting most people, and where it falls mainly on uninhabited land has been part of the presentation that I gave at this year’s SoC meeting in Plymouth (where the delegates witnessed some of the rain from the maps shown below, but enjoyed a little bit of the late summer’s sunshine as well). An animation of these maps and the annual precipitation map have been published on this website last week (see here).
The following series of maps shows monthly precipitation patterns derived from monitored climate data of approximately 50 years (1950-2000, data obtained from http://worldclim.org/). The underlying popoulation grid is a gridded cartogram transformation of the global population distribution population data from SEDAC). As explained in more detail in the previous entry, this representation is a view of how the world’s population is directly exposed to the monthly precipitation patterns, shrinking all those unpopulated parts of the land surface while proportionally increasing the size of land according to the total number of people living there. The choropleth overlay visualises precipitation just as in a conventional map (also shown in the inset map. This shows, when it rains on humanity throughout the year – month by month: Continue reading →